Equipment of such kind generally includes two shoring rods designed to be disposed parallel to one another on either side of the vertebrae to be treated, and assemblies for anchoring these rods to the vertebrae, in the form of hooks or pedicle screws. This equipment may also include cross-members that approach these rods incrementally, for preserving their position relative to one another.
In order to attach a shoring rod to an anchoring assembly, the design has provided for the inclusion of two facing walls on the proximal portion of the anchoring assembly, these walls defining a seating for the rod therebetween and furnished with means, such as a threaded or tapping arrangement, for receiving a nut or threaded plug for locking the rod. These walls impart a “tuning fork” or “tulip” shape to this proximal portion, such names having now become the accepted designations for this type of assembly.
An existing hook on this type of equipment is designed to be engaged around the pedicle and for this purpose is furnished with a curved vane that is shaped correspondingly. However, the possibilities for implementing this hook are limited to one pedicle support point, which does not allow of adaptation for the various situations that may arise. In fact, in certain cases depending specifically on the position and orientation of the shoring rod with respect to this hook or depending on the quality of the vertebral bone, it may be preferable to select a different support area.
In extreme cases, the existing hook may also provoke doubts regarding the perfect resistance of the assembly that it allows.
The object of the present invention is primarily to remedy these essential disadvantages.
In addition, one significant disadvantage of the existing “tuning fork” (“tulip”) hooks is that occasionally considerable effort is required to locate the rods inside the seating for these rods. When the pedicles are small in size, as is the case for thoracic vertebrae, particularly vertebrae D1 to D4, there is a danger that the pedicle may break and it is necessary to rely on hooks rather than screws. In view of the limitations described in the aforegoing, the existing hooks are not ideally suited for all situations that may arise.
A further disadvantage of the existing hooks is that their height is substantial due to the height of the said walls defining the seatings for a shoring rod. This height is not particularly inconvenient when the tissues are fairly thick, as is the case at the level of the lumbar vertebrae, but it does create difficulties when tissues become relatively thin, as is the case at the level of the thoracic vertebrae, when the equipment may be felt under the skin.
A further object of the present invention is to remedy this disadvantage.